JPH11322695A - Production of nitrile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a nitrile useful as an intermediate for medicines, agrochemicals, dyes, pigments, etc., according to a method by which stable production can be carried out without any problems in aspects of safety and operating efficiency by adding and reacting urea with a specific carboxylic acid in a molten state. SOLUTION: (B) Urea is added and reacted with (A) a carboxylic acid represented by the formula R-COOH [R is a (substituted)alkyl, an alkenyl, an alkynyl or the like] in a molten state (e.g. p-toluic acid) preferably in the presence of a catalyst such as a mixture of boric acid with cobalt acetate to produce the objective compound represented by the formula R-CN (e.g. p- tolunitrile). The catalyst is preferably used in an amount of about 0.1-10 wt.% based on the component A. When the cobalt salt is used as the catalyst, the amount of the component B used is preferably <1 mol based on 1 mol of the component A. In the method, a waste gas distillate line is preferably connected to a reactor and heated at >=60 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to the following formula (I)

[0002]

Embedded image The reaction of the carboxylic acid with urea represented by
I)

[0003]

Embedded image (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group).

[0004]

2. Description of the Related Art Nitriles are very important compounds as intermediates for pharmaceuticals, agricultural chemicals, dyes, pigments and the like.

Hitherto, various methods have been known for producing nitriles. Among them, a method for producing nitriles by a reaction between carboxylic acid and urea is a general method (Japanese Patent Publication No. Sho 62-5899). Gazette, JP-A-54-955
No. 41, Organic Synthesis (Organic)
Synthesis) Collective Vol.
4, p. 513 (1963)).

[0006]

However, when nitrile is obtained from the reaction between carboxylic acid and urea, (1) water, carbon dioxide, and ammonia are simultaneously generated and discharged from the reactor through the exhaust gas distillation line to the outside of the system. At that time,
Sublimates such as ammonium bicarbonate and by-products such as ammonium bicarbonate produced under the reaction conditions are discharged and block the exhaust gas line, which increases the internal pressure of the reactor and makes it difficult to ensure safety. Problems that significantly impair workability, such as the need to perform the work of removing
(2) In order to save the trouble of adding urea later, the carboxylic acid and urea are first charged and then heated to carry out the reaction, or in order to improve the dissolution temperature of carboxylic acid, some carboxylic acid is added. After the addition of urea and heating to make it uniform, the remaining urea was added and the reaction was performed, such as when the carboxylic acid and urea coexisted before the start of the reaction. Problems that cannot be ignored from the viewpoint of deterioration of workability, ensuring safety, or adverse effects on the environment, such as rapid reaction and sudden boiling of the contents, and rapid and large generation of exhaust gas such as carbon dioxide and ammonia. (3) To increase the rate of amide formation as an intermediate by almost completely consuming the carboxylic acid as a raw material and the rate of nitrile formation from the subsequent dehydration reaction, You may use an excess of urea to Bonn acid. However, because of this, urea not used in the reaction self-decomposes to give a sublimate, and the exhaust gas line connected to the reaction vessel is blocked, so that the workability is deteriorated or it is difficult to secure safety, and it is stable. There are problems, such as very difficult to perform nitrile production, and the conventional nitrile production method has not always been industrially satisfactory.

[0007]

Means for Solving the Problems The present inventors have studied diligently in order to establish a technology for producing a stable nitrile in a reaction for producing a nitrile from a reaction between a carboxylic acid and urea without any problem in terms of safety and workability. As a result, surprisingly, (1) if urea is added to a carboxylic acid in a molten state or a carboxylic acid completely dissolved in a solvent, bumping of the contents due to a sudden reaction between the carboxylic acid and the urea may occur. It is possible to produce stable nitrile without generating a sudden large amount of exhaust gas such as carbon dioxide and ammonia.
(2) By setting the exhaust gas distilling line connected to the reactor to 60 ° C. or higher, almost no obstruction is caused, and the problem that it is difficult to ensure safety and the problem that workability is significantly deteriorated are solved. (3) If a cobalt salt is used as a catalyst and the amount of urea used is less than 1.0 in molar ratio with respect to carboxylic acid, stable production of nitriles can be achieved without any problematic clogging of exhaust gas lines. It can be carried out,
And found the present invention.

That is, the present invention provides: (1) the following formula (I)

[0009]

Embedded image (Wherein R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group) by reacting a carboxylic acid represented by the following formula (II)

[0010]

Embedded image (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group or aralkyl group) when urea is added to a carboxylic acid in a molten state when the nitrile is produced. A method for producing a nitrile, characterized in that: (2) When producing the nitrile represented by the formula (II) by reacting the carboxylic acid represented by the formula (I) with urea, urea is added to the carboxylic acid dissolved in a solvent. Nitrile manufacturing method. (3) When producing the nitrile represented by the above (II) by the reaction between the carboxylic acid represented by the above formula (I) and urea, the exhaust gas distillation line connected to the reactor is kept at 60 ° C. or higher. A method for producing a nitrile, characterized in that: (4) When producing the nitrile represented by the above (II) by reacting the carboxylic acid represented by the above formula (I) with urea, a cobalt salt is used as a catalyst, and less than 1 mol per mol of the carboxylic acid. A method for producing a nitrile, comprising using urea. It is.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below.

In the present invention, the following formula (I)

[0013]

Embedded image (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group) as a raw material. R represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkenyl group, an alkynyl group, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms. Unsubstituted aralkyl groups are preferred, and more preferably C6 to C20.
Or a substituted or unsubstituted aryl group.

Specifically, lauric acid, stearic acid,
Aliphatic carboxylic acids such as oleic acid, benzoic acid, toluic acid, ethylbenzoic acid, chlorobenzoic acid, dichlorobenzoic acid, bromobenzoic acid, dibromobenzoic acid, anisic acid, ethoxybenzoic acid, dimethoxybenzoic acid, nitrobenzoic acid Aromatic carboxylic acids such as acids, cyanobenzoic acid, aminobenzoic acid, hydroxybenzoic acid, dihydroxybenzoic acid, hydroxymethylbenzoic acid, formylbenzoic acid, phthalic acid, naphthoic acid are used.

These carboxylic acids can be easily produced by known techniques such as gas or liquid phase air oxidation, nitric acid oxidation, electrolytic oxidation, reagent oxidation and the like. In addition, the carboxylic acid as a raw material has no problem if it is used after purifying the product obtained by the above-mentioned method or if it is used without purification.

The exhaust gas distilling line of the present invention refers to a pipe connecting the reactor with a scrubber for capturing exhaust gas. Sublimates such as carbon, water, ammonia, and ammonium bicarbonate, and decomposition products of urea itself are emitted. The material can be used without any particular problem as long as it can withstand these discharged compounds. The heating temperature is 60 ° C. or higher, which is the sublimation temperature of ammonium bicarbonate, which is the main component of the blockage, preferably 60 to 250 ° C.
More preferably, the temperature should be 100 to 220 ° C. There is no particular problem with the heating method as long as the exhaust gas line can be maintained at 60 ° C. or higher.

In the reaction of the present invention, the reaction of a carboxylic acid with urea is first carried out by the following formula (III)

[0018]

Embedded image (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group, and R represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkenyl group, An alkynyl group, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted aralkyl group having 6 to 20 carbon atoms is preferable, and more preferably 6 to 2 carbon atoms.
Up to 0 substituted or unsubstituted aryl groups. ) Is produced, and the desired nitrile is produced by the dehydration reaction. The amide produced as an intermediate may be subjected to a dehydration reaction after isolation and purification, or a crude product may be used as it is, but usually, the crude product is used as it is for the dehydration reaction.

The reaction of the present invention may be carried out in the presence of a catalyst such as an inorganic acid or a cobalt salt. Examples of the inorganic acid include boric acid, phosphoric acid, phosphorous acid, and sulfuric acid. Examples of the cobalt salt include compounds such as cobalt borate, cobalt acetate, cobalt oxide, cobalt chloride, and cobalt sulfate.These compounds may be used alone. May be used, or
Mixtures may be used, but preferred is cobalt borate or a mixture of boric acid and cobalt acetate.
The amount of the catalyst is 0.01 to 30% by weight based on the carboxylic acid,
Preferably, it may be about 0.1 to 10% by weight.

In the reaction of the present invention, urea is preferably added to a molten carboxylic acid or a carboxylic acid completely dissolved in a solvent at such a rate that no rapid reaction with the carboxylic acid occurs. Urea may be added as a solid or in a molten state, or may be added after being dissolved in a solvent inert to the reaction.

The solvent used in the reaction of the present invention can be used without any particular problem as long as it is inert to the reaction between urea and carboxylic acid. For example, cumene, trimethylbenzene, tetramethylbenzene, cymene, diisopropylbenzene , Decalin, tetralin, methylnaphthalene,
Aromatic or aliphatic hydrocarbons such as dimethylnaphthalene, isopropylnaphthalene, diisopropylnaphthalene, chlorotoluene, dichlorotoluene, dichlorobenzene, chloroaromatic compounds such as trichlorobenzene, nitrobenzene, aromatic nitro compounds such as nitrotoluene, Examples thereof include aromatic ether compounds such as diphenyl ether, amide compounds such as dimethylformamide and dimethylacetamide, and sulfur-containing compounds such as dimethyl sulfoxide. The amount is not particularly limited as long as the starting carboxylic acid is dissolved under the reaction conditions. In addition, there is no problem whether a pure product or a reaction and recovery product is used as the solvent.

The amount of urea used in the present invention is preferably less than 1.0 in molar ratio to carboxylic acid, more preferably
0.5 to 1.0. In this case, a cobalt salt is used as the catalyst. Examples of the cobalt salt include compounds such as cobalt borate, cobalt acetate, cobalt oxide, cobalt chloride, and cobalt sulfate, and are preferably cobalt borate or a mixture of boric acid and cobalt acetate. These compounds may be used alone or as a mixture. The amount of catalyst is based on carboxylic acid.
0.01 to 30% by weight, preferably 0.1 to 10% by weight
Degree is fine.

The reaction temperature of the present invention varies depending on the melting point of the starting carboxylic acid, the reactivity, the nature of the solvent, etc., but the first amidation is at 150 to 350 ° C., preferably
170-250 ° C., subsequent nitrilation is 200
To 400 ° C, preferably 220 to 300 ° C. The reaction may be carried out at normal pressure, increased pressure or reduced pressure, but preferably, the first amidation is performed at normal pressure or increased pressure, and the subsequent nitrilation is performed at normal pressure or reduced pressure.

The reaction may be performed in a gas phase or a liquid phase, but is preferably performed in a liquid phase. Further, the reaction may be performed while flowing an inert gas such as nitrogen. The reaction may be carried out batchwise or continuously without any particular problem. In any case, since the reaction is a dehydration reaction, the reaction is preferably performed in a direction of removing generated water. At that point, if the boiling point of the target nitrile is close to this range, the equilibrium is shifted to the product side by using the reactive distillation method of distilling the produced nitrile from the reactor together with the by-product water, and It can be carried out more advantageously in that the produced nitrile can be isolated without thermal degradation.

The nitrile obtained by the method of the present invention is
It can be purified by a conventional method such as distillation and recrystallization.

Hereinafter, the present invention will be described more specifically with reference to examples.

[0027]

(Example 1) A 200-ml four-necked flask equipped with a stirrer, a thermometer, and a gas injection pipe was provided with an exhaust gas distilling pipe heated to 120 ° C. by a ribbon heater up to a trap filled with water. did. There, 100 g of p-toluic acid
(0.73 mol; Tokyo Chemical Special Grade), 2.00 g of cobalt acetate tetrahydrate (1.9 wt% based on p-toluamide;
1.00 g of boric acid (1.9 wt% based on p-toluamide; Katayama Chemical first grade) was charged, and at a reaction temperature of 190 ° C., 33.15 g (0.55 mol;) of urea was 6.75. The mixture was added over time, and further stirred at 190 ° C. for 1.25 hours. When the contents were analyzed by high performance liquid chromatography, the conversion of p-toluic acid was 85.5.
%, The production rate of p-toluamide was 79.4%, and the production rate of p-tolunitrile was 1.5%. Then, the temperature of the product is raised to 240 ° C. as it is, and 80 ml / min.
The reaction was carried out for 9 hours while blowing nitrogen. After the completion of the reaction, the distillate and the residue in the flask were analyzed by high performance liquid chromatography. The conversion of p-toluic acid was 91.5%, the production of p-tolunitrile was 85.2%,
The by-product rate of p-toluamide was 1.3%.

In the present embodiment, there were no phenomena that would hinder the implementation for safety assurance, such as bumping of the contents due to a sudden reaction or rapid and massive blowing of exhaust gas. Also,
No obstruction was found in the distillation tube.

Comparative Example 1 100 g of p-toluic acid and 18 g (0.30 mol) of urea were charged, and 40 g (0.67 mol) of urea was gradually added from 130 ° C., which is the melting point of urea, to 190 ° C. The reaction was carried out in the same manner as in Example 1, except that the reaction was carried out while adding little by little. However, the sudden boiling of the contents due to a sudden reaction occurred on the way, causing problems such as blocking the distilling tube and generating a strong irritating smell of ammonia, which made it difficult to carry out in order to ensure safety. .

Comparative Example 2 A reaction was carried out in the same manner as in Example 1 except that the distillation tube was not heated by the ribbon heater.
However, since the blockage adhered to the distillation pipe, the internal pressure in the reactor increased, or a problem occurred many times, such as the need to stop the reaction midway and remove the blockage in the distillation pipe, The reaction was interrupted. When the clogged material was analyzed by IR, it was found that ammonium bicarbonate, a urea decomposition product, was the main component. (Comparative Example 3) The amount of urea used was 58 g (0.97 mol; p
-Toluic acid in a molar ratio of 1.33),
The reaction was carried out in the same manner as in Example 1. However, clogging occurred in the distillate pipe during the reaction, and the internal pressure in the reactor increased, or the reaction had to be stopped halfway to remove the clogging. Therefore, the reaction was interrupted.

[0031]

According to the manufacturing method of the present invention, the following effects can be obtained. (1) Bumping of contents and rapid and large-volume blowing of exhaust gas due to abrupt reaction become zero, so that nitrile can be produced without any problem in ensuring safety. (2) Occlusion of the exhaust gas line becomes zero due to the reaction between the carboxylic acid and urea, and the nitrile can be produced without any problem in ensuring safety. (3) Due to the reaction between carboxylic acid and urea, urea decomposition products, which are the source of blockages in the exhaust gas line, become zero, and nitrile can be produced without any problem in ensuring safety.

Claims (7)

[Claims] (1) The following formula (I): (Wherein R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group) by the reaction of a carboxylic acid represented by the following formula (II): (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group or aralkyl group) when urea is added to a carboxylic acid in a molten state when the nitrile is produced. A method for producing a nitrile, characterized in that: 2. A compound represented by the following formula (I): (Wherein R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group) by the reaction of a carboxylic acid represented by the following formula (II): (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group or aralkyl group) when producing a nitrile represented by the following formula: A process for producing a nitrile. 3. A compound represented by the following formula (I): (Wherein R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group) by the reaction of a carboxylic acid represented by the following formula (II): (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group) when producing a nitrile represented by the following formula: A nitrile temperature of 60 ° C. or higher. 4. The method for producing a nitrile according to claim 1, wherein an inorganic acid and / or a cobalt salt is used as the catalyst. 5. A compound represented by the following formula (I): (Wherein R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, or aralkyl group) by the reaction of a carboxylic acid represented by the following formula (II): (Wherein, R represents a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group or aralkyl group), a cobalt salt is used as a catalyst and a carboxylic acid A method for producing a nitrile, comprising using less than 1 mole of urea per mole. 6. The method for producing a nitrile according to claim 1, wherein R in the formulas (I) and (II) is an aryl group. 7. The method for producing a nitrile according to claim 1, wherein cobalt borate or a mixture of boric acid and cobalt acetate is used as the catalyst.